Process and Method For Producing Foamable Metals

ABSTRACT

A process for producing foamable metal articles and foamed metal articles and materials. A mixture of foamable material is produced by blending at least one metal powder and one gas-producing blowing agent, then compacting the mixture into a solid form of various cross-sections and configurations. The gas-producing blowing agent comprises silicon powder and talc powder.

TECHNICAL FIELD

The present invention relates to a process for producing foamablematerials. More particularly, the present invention relates to mixturesof foamable metal materials produced from at least one metal powder andone gas-producing blowing agent.

BACKGROUND OF THE INVENTION

The production of foamed metal articles is known in the art. There are avariety of patents and publications concerning the production of foamedmetal articles, devices and processes for producing said articles, andthe metal/foaming agent mixtures used therein. The number ofapplications for foamed metals is high, including, but not limited to,stiffening of hollow structures, sound and vibration dampening,inhibition of energy flows, and creation of decorative elements.

Current methods of closed-cell foamed metal article production, however,typically result in cells that are irregular and coarse, often with the“windows” of the gas bubbles appearing to be fissured. In addition,prior art methods usually result in a substantial amount of unfoamedmetal material at the base of the foamed metal article.

Accordingly, there is a need in the art for an improved metal/foamingagent mixture and process for the production of foamed metal articles,that results in more thorough and consistent cell formation in thefoamed metal article.

SUMMARY OF THE INVENTION

This invention is directed to an improved process for producing foamableand foamed metal articles, and an improvement of the industrialproperties of the foamable products and of the closed-cell foamed metalarticles by comparison with the prior art.

In one exemplary embodiment, the present invention comprises a processfor producing foamable metal articles, the process comprising producinga mixture of at least one metal powder and a gas-producing blowingagent, and compacting the mixture to a semi-finished foamable product oraticle, wherein the gas-producing blowing agent mixture contains somecombination of silicon powder and/or talc powder (Si, [H₂Mg₃(SiO₃)₄] or[Mg₃Si₄O₁₀(OH)₂]).

In another exemplary embodiment, the present invention comprises aprocess of producing a foamed metal article, the process comprisingsubjecting the aforesaid compacted mixture and/or foamable product toconditions (e.g., elevated temperature, and/or elevated or reducedpressure) effective to foam said mixture.

In yet another exemplary embodiment, the present invention comprises thefoamable metal articles produced by said processes.

Still other advantages of various embodiments will become apparent tothose skilled in this art from the following description wherein thereis shown and described exemplary embodiments of this invention simplyfor the purposes of illustration. As will be realized, the invention iscapable of other different aspects and embodiments without departingfrom the scope of the invention. Accordingly, the advantages, drawings,and descriptions are illustrative in nature and not restrictive innature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a process for producing foamablemetal articles and foamed metal articles in accordance with an exemplaryembodiment of the present invention.

FIGS. 2 and 3 show a cross-section of a foamed metal article produced inaccordance with one embodiment of the present invention.

FIG. 4 shows a cross-section of a foamed metal article produced inaccordance with prior art techniques.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows an exemplary embodiment of a process for producing foamablemetal articles and foamed metal articles in accordance with the presentinvention. At least one metal powder 10 is mixed with a gas-producingblowing agent 12 containing some combination of silicon powder and/ortalc powder (Si, [H₂Mg₃(SiO₃)₄] or [Mg₃Si₄O₁₀(OH)₂]). While othergas-producing blowing agents (e.g., titanium hydride, carbonates, andhydrates) have been used for producing foamable metal articles, the useof silicon powder or talc powder, or a combination of both, is not knownin the art.

The combination of the metal powder 10 and the gas-producing blowingagent 12 is blended 20 and compacted 30 to form compressed foamablemetal articles 40 useful for producing foamed metal articles 70. Thefoamable metal articles then may be exposed to elevated temperature 50,and/or elevated or reduced pressure, effective to cause the foamablemetal article to foam. The material is then cooled 60, if necessary. Inan alternative embodiment, the foamable metal article is placed in amold 50 and foamed therein.

The foamed metal articles produced with the aid of the gas-producingblowing agent 12 in accordance with the present invention, especiallyproduced auto-catalytically, have a morphology differing from that offoams obtained using prior art foaming agents (for example, titaniumhydride). The foamed metal articles obtained by means of the processdescribed herein have a very homogenous pore density distributionextending into the surface regions of the shaped foamed metal article,as seen in FIGS. 2 and 3. FIGS. 2 and 3 show an aluminum foamed productproduced according to the present invention using 10% Silicon powder and1% Talc powder as the gas-producing blowing agent mixture, andalumininum metal powder (percentages are by weight of the blendedmixture).

This represents a considerable advance over foamed metal articles formedusing prior art methods and prior art gas-producing blowing agents. Anexample of an aluminum foamed metal article produced using prior arttechniques, using 1% titanium hydride as the gas-producing blowingagent, is shown in FIG. 4. The compaction and foaming conditions wereidentical with the process used to produce the article shown in FIGS. 2and 3.

FIGS. 2 through 4 show a cross-section of the respective foamed metalarticles, cut transversely. The foamed metal article produced usingtitanium hydride in accordance with the prior art shows extensivecompaction (i.e., a substantial layer of unfoamed material) of the basezone 30 along the bottom of the article (see FIG. 4). The celldistribution in the foamed structure is very irregular, and the cellsthemselves are mainly coarse, and some have risen. This results in asomewhat fissured surface of the metal article, where large gas bubblesof this type have “blown off” on the surface.

In contrast, the foamed article produced in accordance with the presentinvention (shown in FIGS. 2 and 3) distinctly shows more uniformfoaming. The compacted base zone in this article 26 is onlyapproximately 0.25 mm thick, a marked improvement over the up to 10 mmthick base zone 30 shown in the prior art material (FIG. 4). Inaddition, the number of cells per unit volume in the foamed articleproduced in accordance with the present invention is distinctly greater,specifically with preference for the presence of small cells 28.Irregularity of cells is distinctly less pronounced than in theprior-art article, and the openings are finer and more uniform.

Examination of the structures of the cells in the foamed articles shownin FIGS. 2-4 reveals a peculiarity of the prior art metal foam (FIG. 4).As seen in FIG. 4, the openings in the “windows” of the gas bubblesfrequently appear to be fissured 32, whereas virtually no such sites areevident in the foam of the present invention (FIGS. 2 and 3). Thisindicates that, at the time when the volume of the metal changed, theviscosity of the material foamed according to the prior art is less thanthat of the material foamed according to the invention. A possiblereason for this is that titanium hydride increases the viscosity of thesurrounding metal (in this case, aluminum), while the gas-producingblowing agent of the present invention has had a contrary effect.

It is possible to foam all fusible metals or metal alloys in accordancewith the method described herein. In one exemplary embodiment, the metalpowder particularly preferably employed for the purpose of the presentinvention is aluminum and its alloys. In this embodiment, the metalpowder comprises essentially aluminum, and where appropriate,conventional alloying constituents including, but not limited to,magnesium, copper, and/or silicon.

Thus, it should be understood that the embodiments and examples havebeen chosen and described in order to best illustrate the principles ofthe invention and its practical applications to thereby enable one ofordinary skill in the art to best utilize the invention in variousembodiments and with various modifications as are suited for particularuses contemplated. Even though specific embodiments of this inventionhave been described, they are not to be taken as exhaustive. There areseveral variations that will be apparent to those skilled in the art.Accordingly, it is intended that the scope of the invention be definedby the claims appended hereto.

1. A process for producing a foamed metal article, comprising the stepsof: blending a mixture of at least one metal powder and onegas-producing blowing agent; and compacting the mixture to form afoamable metal article, wherein the gas-producing blowing agentcomprises one or more reactive powder materials.
 2. The process of claim1, wherein the gas-producing blowing agent comprises silicon powder ortalc powder or a combination thereof.
 3. The process of claim 1, whereinthe metal powder comprises essentially aluminum, or aluminum alloyedwith one or more conventional alloying constituents.
 4. The process ofclaim wherein the compacting is carried out by rolling, extrusion, or acombination of both.
 5. The process of claim 1, wherein the compactingis carried out below the decomposition temperature of the gas-producingblowing agent mixture.
 6. The process of claim 1, wherein the compactingis carried out at room temperature.
 7. The process of claim 1, whereinthe mixture is compacted to a density of at least 90% of the theoreticaldensity of the metal in the metal powder.
 8. The process of claim 1,wherein the mixture is compacted to a density of at least 95% of thetheoretical density of the metal in the metal powder.
 9. The process ofclaim 1, wherein the gas-producing blowing agent is from 0.1% to 12% byweight of the mixture.
 10. The process of claim 1, further comprisingthe step of: exposing the foamable metal article to elevatedtemperature, and/or elevated or reduced pressure, effective to cause thefoamable metal article to foam.
 11. The process of claims 1, furthercomprising the steps of: placing said foamable metal article in a mold;and exposing the foamable metal article to elevated temperature, and/orelevated or reduced pressure, effective to cause the foamable metalarticle to foam.
 12. A foamable metal article produced by the process ofclaim
 1. 13. A foamed metal article produced by the process of claim 10.